Loans Receivable and Allowance for Loan Losses (Summary of Impaired Loans Receivable by Class) (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	$ 62,113	$ 59,053
Recorded Investment	53,481	52,019
Average Recorded Investment	56,048	52,002
Interest Income Recognized	391	1,486
Residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	25,721	24,860
Recorded Investment	22,179	21,401
Related Allowance	1,728	1,716
Average Recorded Investment	22,278	21,732
Interest Income Recognized	243	1,003
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	5,682	5,694
Recorded Investment	5,554	5,633
Related Allowance	152	270
Average Recorded Investment	5,691	5,697
Interest Income Recognized	13	95
Construction [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,553	2,553
Recorded Investment	2,517	2,517
Related Allowance	0	0
Average Recorded Investment	2,517	2,514
Interest Income Recognized	0	0
Mortgage Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	33,956	33,107
Recorded Investment	30,250	29,551
Related Allowance	1,880	1,986
Average Recorded Investment	30,486	29,943
Interest Income Recognized	256	1,098
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	25,223	23,211
Recorded Investment	20,823	20,255
Related Allowance	1,050	268
Average Recorded Investment	23,132	19,774
Interest Income Recognized	104	263
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,934	2,735
Recorded Investment	2,408	2,213
Related Allowance	102	80
Average Recorded Investment	2,430	2,285
Interest Income Recognized	31	125
Loans With No Related Allowance [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	37,518	38,123
Recorded Investment	30,038
Related Allowance	0	0
Average Recorded Investment	32,494	26,971
Interest Income Recognized	201	842
Loans With No Related Allowance [Member] | Residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	10,700	10,691
Recorded Investment	8,229	7,881
Related Allowance	0	0
Average Recorded Investment	8,270	8,027
Interest Income Recognized	113	484
Loans With No Related Allowance [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	4,600	1,556
Recorded Investment	4,472	1,556
Related Allowance	0	0
Average Recorded Investment	4,606	1,586
Interest Income Recognized	0	40
Loans With No Related Allowance [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	2,553	2,553
Recorded Investment	2,517	2,517
Related Allowance	0	0
Average Recorded Investment	2,517	2,514
Interest Income Recognized	0	0
Loans With No Related Allowance [Member] | Mortgage Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	17,853	14,800
Recorded Investment	15,218	11,954
Related Allowance	0	0
Average Recorded Investment	15,393	12,127
Interest Income Recognized	113	524
Loans With No Related Allowance [Member] | Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	18,191	21,830
Recorded Investment	13,861	18,874
Related Allowance	0	0
Average Recorded Investment	16,130	13,818
Interest Income Recognized	76	259
Loans With No Related Allowance [Member] | Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,474	1,493
Recorded Investment	959	981
Related Allowance	0	0
Average Recorded Investment	971	1,026
Interest Income Recognized	12	59
Loans With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	24,595	20,930
Recorded Investment	23,443	20,210
Related Allowance	3,032	2,334
Average Recorded Investment	23,554	25,031
Interest Income Recognized	190	644
Loans With Allowance Recorded [Member] | Residential [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	15,021	14,169
Recorded Investment	13,950	13,520
Related Allowance	1,728	1,716
Average Recorded Investment	14,008	13,705
Interest Income Recognized	130	519
Loans With Allowance Recorded [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,082	4,138
Recorded Investment	1,082	4,077
Related Allowance	152	270
Average Recorded Investment	1,085	4,111
Interest Income Recognized	13	55
Loans With Allowance Recorded [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	0	0
Recorded Investment	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Loans With Allowance Recorded [Member] | Mortgage Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	16,103	18,307
Recorded Investment	15,032	17,597
Related Allowance	1,880	1,986
Average Recorded Investment	15,093	17,816
Interest Income Recognized	143	574
Loans With Allowance Recorded [Member] | Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	7,032	1,381
Recorded Investment	6,962	1,381
Related Allowance	1,050	268
Average Recorded Investment	7,002	5,956
Interest Income Recognized	28	4
Loans With Allowance Recorded [Member] | Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,460	1,242
Recorded Investment	1,449	1,232
Related Allowance	102	80
Average Recorded Investment	1,459	1,259
Interest Income Recognized	$ 19	$ 66